Encoding standards often use recursion to compress data. In recursion, data is encoded as a mathematical function of other previous data. As a result, when decoding the data, the previous data is needed.
An encoded picture is often assembled in portions. Each portion is associated with a particular. region of the picture. The portions are often decoded in a particular order. For decoding some of the portions, data from previously decoded portions is needed.
A video decoder typically includes integrated circuits for performing computationally intense operations, and memory. The memory includes both on-chip memory and off-chip memory. On-chip memory is memory that is located on the integrated circuit and can be quickly accessed. Off-chip memory is usually significantly slower to access than on-chip memory.
During decoding, storing information from portions that will be used for decoding later portions in on-chip memory is significantly faster than storing the information off-chip. However, on-chip memory is expensive, and consumes physical area of the integrated circuit. Therefore, the amount of data that on-chip memory can store is limited. In contrast, decoded video data generates very large amounts of data. Therefore, it may be impractical to store all of the decoded data on-chip.
The data needed for decoding a portion is typically contained in the neighboring portions that are decoded prior to the portion, such as the left neighbor. In many decoding orders, the left neighboring portion is decoded either immediately prior to the portion or shortly prior to the portion. In such a case, it can be possible to store some of the information from each portion for use in decoding the portions right neighbor.
However, the information needed from the left neighboring portion may not be determinable until after decoding the right neighboring portion.
Other limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.